To enable video images picked up with a video camera or the like to be seen comfortably, techniques for keeping the camera horizontal have been proposed. For example, Japanese Patent Laid-Open No. 64-40824 discloses that a horizontality detector detects an inclination of the camera to display information corresponding to the detected inclination on a display device to notice and warn the user of the inclination of the camera. Further, for the display of the inclination, a proposal has been made of, for example, a technique for displaying a horizontal reference line and the inclination of the camera in different colors, and if they match, displaying them as a single line as disclosed in Japanese Patent Laid-Open No. 2002-271654.